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Analog Devices Semiconductor Electronic Components Datasheet

ADP1878 Datasheet

Synchronous Buck Controller

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ADP1878 pdf
Data Sheet
Synchronous Buck Controller with
Constant On Time and Valley Current Mode
ADP1878/ADP1879
FEATURES
Power input voltage range: 2.95 V to 20 V
On-board bias regulator
Minimum output voltage: 0.6 V
0.6 V reference voltage with ±1.0% accuracy
Supports all N-channel MOSFET power stages
Available in 300 kHz, 600 kHz, and 1.0 MHz options
No current sense resistor required
Power saving mode (PSM) for light loads (ADP1879 only)
Resistor programmable current limit
Power good with internal pull-up resistor
Externally programmable soft start
Thermal overload protection
Short-circuit protection
Standalone precision enable input
Integrated bootstrap diode for high-side drive
Starts into a precharged output
Available in a 14-lead LFCSP_WD package
APPLICATIONS
Telecommunications and networking systems
Mid-to-high end servers
Set-top boxes
DSP core power supplies
GENERAL DESCRIPTION
The ADP1878/ADP1879 are versatile current-mode, synchronous
step-down controllers. They provide superior transient response,
optimal stability, and current-limit protection by using a constant
on time, pseudo fixed frequency with a programmable current-limit,
current control scheme. These devices offer optimum performance
at low duty cycles by using a valley, current-mode control architec-
ture allowing the ADP1878/ADP1879 to drive all N-channel power
stages to regulate output voltages to as low as 0.6 V.
The ADP1879 is the power saving mode (PSM) version of the
device and is capable of pulse skipping to maintain output
regulation while achieving improved system efficiency at light
loads (see the ADP1879 Power Saving Mode (PSM) section for
more information).
Available in three frequency options (300 kHz, 600 kHz, and
1.0 MHz) plus the PSM option, the ADP1878/ADP1879 are well
suited for a wide range of applications that require a single input
power supply range from 2.95 V to 20 V. Low voltage biasing is
supplied via a 5 V internal low dropout regulator (LDO). In
addition, soft start programmability is included to limit input
inrush current from the input supply during startup and to
provide reverse current protection during precharged output
Rev. A
Information furnished by Analog Devices is believed to be accurate and reliable. However, no
responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other
rights of third parties that may result from its use. Specifications subject to change without notice. No
license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
Trademarksandregisteredtrademarksarethepropertyoftheirrespectiveowners.
TYPICAL APPLICATIONS CIRCUIT
VIN = 2.95V TO 20V
CC
RC CC2
VREG
VOUT
10k
RTOP
RBOT
CVREG2
CVREG
RRES
VIN
ADP1878/
ADP1879
COMP
BST
EN
FB
GND
VREG
DRVH
SW
DRVL
RES
PGOOD
SS
PGND
CIN
CBST
Q1 L
COUT
Q2
RPGD
VEXT
CSS
VOUT
LOAD
Figure 1.
conditions. The low-side current sense, current gain scheme and
integration of a boost diode, together with the PSM/forced
pulse-width modulation (PWM) option, reduce the external
device count and improve efficiency.
The ADP1878/ADP1879 operate over the −40°C to +125°C
junction temperature range and are available in a 14-lead
LFCSP_WD package.
100
95 VIN = 5V (PSM)
90
85
80
75
70 VIN = 16.5V
65
60 VIN = 13V
55 VIN = 13V (PSM)
50
45
40 VIN = 16.5V (PSM)
35
30
25
10
100
TA = 25°C
fVSOWUT=
= 1.8V
300kHz
WÜRTH INDUCTOR:
744325120, L = 1.2µH, DCR = 1.8m
INFINEON FETs:
BSC042N03MS G (UPPER/LOWER)
1k 10k 100k
LOAD CURRENT (mA)
Figure 2. ADP1878/ADP1879 Efficiency vs. Load Current (VOUT = 1.8 V, 300 kHz)
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
www.analog.com
Fax: 781.461.3113 ©2011–2012 Analog Devices, Inc. All rights reserved.


Analog Devices Semiconductor Electronic Components Datasheet

ADP1878 Datasheet

Synchronous Buck Controller

No Preview Available !

ADP1878 pdf
ADP1878/ADP1879
TABLE OF CONTENTS
Features .............................................................................................. 1
Applications....................................................................................... 1
Typical Applications Circuit............................................................ 1
General Description ......................................................................... 1
Revision History ............................................................................... 2
Specifications..................................................................................... 3
Absolute Maximum Ratings ....................................................... 5
Thermal Resistance ...................................................................... 5
ESD Caution.................................................................................. 5
Pin Configuration and Function Descriptions............................. 6
Typical Performance Characteristics ............................................. 7
Theory of Operation ...................................................................... 17
Block Diagram ............................................................................ 17
Startup.......................................................................................... 18
Soft Start ...................................................................................... 18
Precision Enable Circuitry ........................................................ 18
Undervoltage Lockout ............................................................... 18
On-Board Low Dropout (LDO) Regulator............................. 18
Thermal Shutdown..................................................................... 19
Programming Resistor (RES) Detect Circuit.......................... 19
Valley Current-Limit Setting .................................................... 19
Hiccup Mode During Short Circuit......................................... 21
Synchronous Rectifier................................................................ 21
ADP1879 Power Saving Mode (PSM)...................................... 21
Timer Operation......................................................................... 22
REVISION HISTORY
6/12—Rev. 0 to Rev. A
Changes to Table 1.............................................................................3
7/11—Revision 0: Initial Version
Data Sheet
Pseudo Fixed Frequency............................................................ 22
Power-Good Monitoring........................................................... 23
Applications Information .............................................................. 24
Feedback Resistor Divider ........................................................ 24
Inductor Selection ...................................................................... 24
Output Ripple Voltage (ΔVRR) .................................................. 24
Output Capacitor Selection....................................................... 24
Compensation Network ............................................................ 25
Efficiency Consideration........................................................... 26
Input Capacitor Selection.......................................................... 27
Thermal Considerations............................................................ 27
Design Example.......................................................................... 29
External Component Recommendations.................................... 31
Layout Considerations................................................................... 33
IC Section (Left Side of Evaluation Board)............................. 35
Power Section ............................................................................. 35
Differential Sensing.................................................................... 36
Typical Application Circuits ......................................................... 37
12 A, 300 kHz High Current Application Circuit.................. 37
5.5 V Input, 600 kHz Current Application Circuit ................ 37
300 kHz High Current Application Circuit ............................ 38
Packaging and Ordering Information ......................................... 39
Outline Dimensions................................................................... 39
Ordering Guide .......................................................................... 40
Rev. A | Page 2 of 40


Part Number ADP1878
Description Synchronous Buck Controller
Maker Analog Devices
Total Page 30 Pages
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